Evaluation of high-voltage circuit breaker performance with a validated arc model

A digital current-zero measuring system was used to monitor about 200 zero crossings of short-line fault currents in three designs of commercial high-voltage circuit breakers. The breakers were subjected to standard IEC 60056 tests in a high-power laboratory. With these results, an empirical arc model was derived, based on the series connection of three classical modified Mayr models. It was found that only three 'free' parameters, extracted from the arc voltage and current during the pre-zero period can describe the state of the breaker after each test. With this model, the margin of the interrupting capability could be directly obtained. A strong relation between this margin and the arc conductivity at current zero can be established. Independent of arcing time, arcing current and state of the breaker, it was found that the current zero conductivity must decrease to 1-2 ms (only depending on the design of the breaker) to make a successful interruption possible.